The instantaneous water heaters, better known as "gas calefons", present several problems leading to deterioration risks of the apparatus when, for example, the water flow is drastically reduced and the gas flow control valve does not quickly operate which results in the over heating of the heating coil and an almost certain meltdown of the heating coil or even the explosion of the water heater. Another problem of a high potential risk to the user is the posibility of the heater operating in a closed and/or unventilated ambient area which in several opportunities has resulted in intoxication or asfixiation of the user sometimes resulting in death.
Another problem in the known water heaters is the obstruction of the inner passages of the gas valve and/or the operating difficulty of the valve spools due to the binding effect produced by the solid particles entrained in the combustible gas. A further problem in water heaters provided with water temperature themostatic control is the use of a plurality of pivots and levers for interconnecting the thermostatic element to the main gas control valve which makes the correct modulation of the gas flow difficult as a function of the amount of the water flowing through the heating coil and the temperature of the hot water discharge and further increases the manufacturing cost of the gas valve due to the difference machining steps and/or difficult mould casting of the valve body.
The object of the present invention is to provide an improved instantaneous water heater wherein the cited problems are eliminated by the use of known and conventional elements, which elements up to date have never been used in the prior art instantaneous water heaters.
The present invention provides:
a) A solution to the problem of the risk of an explosion of the heating coil due to excesive water heating, by means of a heat sensing element disposed inside the heating coil and activating an interrupting means connected in series to the electromagnetic actuator of the primary gas flow solenoid valve so that in the event the temperature inside the heating coil raises above a predetermined level the solenoid valve interrupts the gas flow thus shutting-off the water heater burner as well as the associated pilot flame and the water heater going to a fail-safe condition.
b) A solution to the problem of generation of an oxygen deficient atmosphere and/or high CO--CO.sub.2 content atmosphere when the water heater operates in a closed or un-ventilated space through the provision of an "ambient analyzer" device which includes the pilot flame for heating the thermocuple that energizes the primary gas flow solenoid valve, said device mantaining the lighted pilot flame as long as the oxygen content of the ambient air is not decreased by more of 3%, the pilot flame being turned-off if the oxygen content is reduced below said level considered as unsafe or harmful to the human beings, said pilot flame light-off cooling the thermocouple and producing the inmediate shut-off of the solenoid gas valve thus turning-off the main burner and the pilot flame with the water heater going to a fail-safe condition.
c) A solution to the problem of entrainment and settling of the solid particles carried by the combustible gas, by the provision of a settling chamber positioned in the body of the gas control valve wherein the solid particles are separated by settling and are further retained by a screen filter.
d) A linear mounting and actuating arrangement between the manual gas closure/opening disk, the manual water temperature regulating means located in the exterior of the main control valve, and the thermostatic element responsive to the water temperature sensed by the thermostatic sensor bulb located inside the heat exchanger, thus eliminating the problems associated to the mechanical transmission by means of levers and simplifying the manufacturing process of the main control valve, which in turn reduces the manufacturing costs and increases the operating reliability of the valve.